It's hot for a reason. The bottom guy allows the top to make him hot, to make him sexually turned on for him so that the bottom facilitate the top easier ultimately, with an exchange of fluids, meaningful to their relationship. Notice the top is very assertive, consistently throughout almost propagating his bottom. It's more than just his bottom, but more so to ensure viability for a next generation in terms of nature, especially if they were a heterosexual couple. Notice also, while the bottom is on his back, the top consistently and constantly fletches during sexual intercourse. His penis is engorged, erect, with a nice girth and is constantly in motion as if he was guiding, directing, ensuring, asserting himself for the preparation of the delivery of semen to his bottom by consistently stimulating him through copulation. This sexual act isn't vulgar, but fascinating in itself. The bottom responds twice with an orgasm overall, the top delivers his semen on his face, nurturing in the final act of propagating their relationship. The bottom is consistently receptive throughout. Notice that in the beginning, the top assertively disciplines the bottom to conform to him to receive him. The bottom perceives this as a sexual stimulation to open to him, to receive him, and ultimately to receive his semen in terms on nature to ensure a next generation, especially if the two are a heterosexual couple.